1. Field of the Invention
The present invention relates to means to control a drive mechanism including a clutch and adapted to act in response to the heat in a prime mover such as a vehicle engine and to control drive of a vehicle accessory, such as a fan mechanism.
2. Prior Art
The problem of controlling heat dissipation devices in connection with a vehicle engine or prime mover so as to keep the prime mover below a predetermined maximum temperature, and at the same time minimizing horse power losses due to operation of the heat dissipation device has resulted in a number of solutions. Prior approaches include those disclosed in U.S. Pat. Nos. 3,804,219 and 3,848,622 of common assignee which show a structure utilizing a separate pressure supply source to provide a temperature responsive and continuously modulated actuation of a clutch mechanism to drive a vehicle fan, the fan speed thus being variations in temperature conditions by controlling continuously the actuating pressure. Other devices known in the art, provide simple on-off devices, acting in response to temperature to actuate a switch, and for shutters in connection with the heat exchange device which may open or close in response to temperature.